How to set up mixed point sources correctly

I want to calculate the flux of photons of multiple energies across the shell,The photon energies are 0.5MeV, 1MeV and 1,5 MeV respectively!
source programming:

Source-newgen.f is then compiled, But there doesn’t seem to be any flux counts。
source_newgen.f (18.7 KB)
sphere energy.flair (2.2 KB)

Hello Fengfeng,

I assume that you will need an isotropic source, and you will need to score the energy spectra of photons exiting the thin water shell. Is it correct? If so, the solution is fairly simple and does not require any user defined source. I would suggest the following:

  1. You start with a #DEFINE card, in this variable you put the nominal energy of the starting photons.
  2. (IMPORTANT) You put the value of such energy in the BEAM card, not you haven’t put anything there and FLUKA assumes zero. You could skip the first point and hard-code it here, but I would always suggest to keep all the variables aside, so it is easier to loop over these.
  3. Still in the BEAM card, you chose the ISOTROPIC option for the divergence of the beam.
  4. I would put the scoring from the “surface” to the “VOID” region, not from the “Vacuum” to the surface.
    I will attach here a working example of the input file.

Nevertheless, I would like to make a quick comment about the routine you choose to adopt. It seems to me that the routine has not been actually implemented: by reading it it is basically the “clean” user routine provided in the FLUKA source code.
Basically, when the produced executable calls the routine, nothing happens. In particular, the big main error is that in the BEAM card the energy is not defined (i.e. equal to zero).

In any case, even if you decide to adopt user defined sources in your simulations, it is always a good practice to put the highest energy you could expect in the BEAM card.
Double check also your EMFCUTS: this is not a really expensive simulation, maybe you could lower them a bit. Perhaps you could also put a production cut, since you only put a transport one.
dcalzola_sphere energy.inp (1.4 KB)

Let me know in case of doubts. Cheers,

Thanks for the expert’s answer. As the teacher said, how can I achieve in the definition card:
1MeV、1.5MeV、2MeV( Emissivity is assumed to be 1)——This is a mixed point source

Hi Fengfeng,

In your specific case, you can take advantage of the special source BEAMSPOT in combination with the cards SPOTBEAM and SPOTPOS. I strongly encourage you to read the SPECSOUR dedicated page in the fluka manual, it is very helpful to understand some of the FLUKA sources capability.

So, applied to your specific case, I have used such card for setting the three different sources energy:
dcalzola_sphere_energy_multiple.inp (2.0 KB)

Good luck with your studies!

Dear Expert,

Thank you very much for your writing,Now for a mixed point source of three energies,After the FLUKA program is normalized, is the probability of each energy corresponding to 1/3? ( According to my personal understanding)

Thank you, teacher!

Hi Fengfeng,

Since (in this example) all the weights applied are the same, your understanding is correct.


Thanks for your reply! :grinning: